1. Field of the Invention
The present invention relates to an ink jet printing apparatus, and, in particular, to an ink jet printing apparatus that performs printing by discharging, onto a recording medium, an ink and a liquid composition that renders a coloring material in the ink insoluble or flocculated.
2. Description of the Related Art
Conventionally, it is well-known that, for an ink jet printing apparatus, a liquid compound (hereinafter also referred to as a “reaction liquid”) that reacts with ink, rendering the coloring material in the ink insoluble or flocculated, is employed in order, for example, to improve water repellency, durability and the development of color on a printed image.
Sometimes, however, with such an ink jet printing apparatus, tiny floating droplets, constituent components of a mist generated when ink and a reaction liquid are discharged from an ink jet head, are attached to and coagulate on a surface in the vicinity of discharge ports formed in a face (hereinafter also referred to as a face surface) of the ink jet head. Further, the ink and the reaction liquid, or a mixture thereof, may splash back from the surface of a print medium, and the constituent components of a product, generated by the reaction of the ink with the reaction liquid, may attach themselves to and coagulate on the face surface. The reaction product thus coagulated near a discharge port could directly cause the clogging of the ink discharge port and a deviation (hereinafter also referred to as deflection) in the ink discharge direction. Furthermore, ink could be attached around the reaction product on the face surface, until it reaches the discharge port, so that a discharge failure or the deflection of the discharge direction could occur. Due to a discharge failure, for example, the deterioration of printing quality could occur. Furthermore, the above described problems could also be caused by ink and reaction liquid that leak from a discharge port.
In order to prevent the clogging of an ink discharge port due to the evaporation of an ink solvent and the deterioration of printing quality due to deflection, and also to recover to an appropriate discharge condition, a conventional ink jet printing apparatus performs various recovery operations, such as capping, suction, cleaning and wiping, using a rubber blade (hereinafter also referred to simply as wiping), and rubbing of a face surface (hereinafter also referred to simply as rubbing) using a rubbing member that employs an absorption material or a porous material.
For example, one conventional ink jet printing apparatus performs a recovery process using a cleaning liquid (see Japanese Patent Laid-Open Publication Nos. Sho 57-125059, Sho 57-133074 and Sho 62-25055). However, this method is not effective for a coagulated product generated by the reaction of ink with a reaction liquid.
Furthermore, a cleaning agent containing, at the least, an organic solvent, a surfactant and water is also well-known (see Japanese Patent Laid-Open Publication No. Hei 4-115954). However, this method is not considered adequate for the removal of a reaction product coagulated on a face surface.
Another means has been proposed whereby, after a discharge operation to be performed for a predetermined period has been completed, a liquid solvent is applied to the face surface of an ink jet head to dissolve a coagulated product thereon, and once the product has been dissolved, it is removed by wiping (see Japanese Patent Laid-Open Publication No. Hei 10-151759). However, since once the product has coagulated on the face surface it can not easily be dissolved, even after the liquid solvent has been applied and the wiping has been performed, traces of the product remain.
Recently, the trend is to form dots having reduced diameters in order to improve the quality of images, and thus, only small amounts of ink, i.e., small ink droplets, are discharged from ink discharge ports. Since the ink droplets are so small in size, they tend to form a floating mist and to be attached to the face surface. Accordingly, a coagulated product tends to be generated.
For an ink jet printing apparatus employing ink and a reaction liquid, generally, separate caps and blades, used for a suction recovery process and for wiping, are prepared for ink use and for reaction liquid use. This is because when only one cap is employed to perform, at the same time, suction for a discharge face from which a reaction liquid is discharged and for a discharge face from which ink is discharged, the reaction liquid and the ink would react with each other in the cap, and the product generated by the reaction would be attached to the face surface. Likewise, were only one blade to be employed for wiping both the reaction liquid discharge face and the ink discharge face, the reaction liquid and the ink attached to the blade would react with each other, and a reaction product would be generated. Therefore, to avoid the generation of a reaction product, separate caps and blades are prepared for reaction liquid use and for ink use, and recovery operations for a reaction liquid head and an ink head are performed separately, not at the same time. In many cases, the recovery process is performed for ink first, and then, the recovery process is performed for the reaction liquid.
As is described above, for an ink jet printing apparatus employing a reaction liquid and ink, since the coagulated reaction product on the face surface is comparatively strong, the product cannot be fully removed by applying the liquid solution, and traces will remain on the face surface. As a result, attaining a satisfactory discharge is difficult. Especially after wiping has been completed, the reaction product may be spread out and remain as a stain on the face surface, and removing such a stain is more difficult.
In addition, after a liquid solution has been applied to the face surface, a certain period of time must elapse before the dissolution of the reaction product is sufficient to permit it to be easily removed from the face surface. Further, once the reaction product has been generated, even though it can be easily removed by applying the liquid solution, a wiping operation for scraping off the reaction product is still required. Therefore, compared with the case wherein ink attached to the face surface is removed simply by wiping, the number of times wiping is performed is increased. As is described above, a certain period of time is required to remove the generated reaction product on the face surface. When this processing is performed repeatedly, each time the printing of a predetermined amount of data is performed, the period required for the processing of all the print data is extended, and this is a problem that is exacerbated by the printing speed.
Furthermore, since an operation for scraping off the thus generated reaction product is performed using a comparatively hard blade and a force that exceeds that required for removing ink, scratching of the face surface tends to occur. And damage to the face surface is a factor that tends to reduce the durability of an ink jet head.
Further, for an ink jet printing apparatus employing a reaction liquid and ink, since removal of a reaction product that cannot be removed simply by wiping is also attempted during the other recovery processing, there is a trend for the period required for each recovery process to be extended, so it is longer than that for an ink jet printing apparatus that employs only ink. Especially, the number of times the suction recovery operation is performed is increased, and exceeds that required for an apparatus that employs only ink, i.e., the amount of ink consumed at times other than during printing is increased, which is very uneconomical.